There are a few things you could check for:

1) Silicon precipitates and/or dendrites in your nitride film.
2) Stress induced defects from the SiNx film. (film stress should be less
than 1 GPa)
3) Silicon defects (i.e. stacking faults, O2 precipitates, lattice damage)
propagating to the gate stack.

A look at the cross sections would tell a bit more.

Good luck,

Eric Miller
Laboratory Manager
Washington Technology Center
Ph:  206 616-3855
www.watechcenter.org


-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of
Campe, Steve
Sent: Thursday, June 03, 2004 5:07 AM
To: '[email protected]'
Subject: [mems-talk] Pinholes in Oxide/Nitride

Hi.
I have a problem with a process which is based on CMOS technology. The
structure consists of a silicon substrate with heavy doping, coated with
thermal (gate) oxide - 85nm, then coated with a similar thickness of
Nitride. A Polysilicon electrode is placed on top of the Nitride. A further
2 Poly electrodes are subsequently patterned which overlap Poly 1 - CCD
device.
I am getting shorts between the first poly and the substrate. De-layering
and SEM inspections shows very small pinholes in the Nitride/Oxide (approx
200nm). These were made visible only by severe poly wet etching. This leaves
a square void under the pinhole.  It does not appear at any of the Poly 2 or
3 stages and so seems to rule out defects in the gate ox, which I would
expect to be randomly distributed.

Thanks

_______________________________________________
[email protected] mailing list: to unsubscribe or change your list
options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
Hosted by the MEMS Exchange, providers of MEMS processing services.
Visit us at http://www.memsnet.org/